U.S. patent number 7,905,287 [Application Number 11/109,354] was granted by the patent office on 2011-03-15 for methods of using a polymeric precipitate to reduce the loss of fluid to a subterranean formation.
This patent grant is currently assigned to Halliburton Energy Services Inc.. Invention is credited to Kenneth W. Oyler, Carl J. Thaemlitz.
United States Patent |
7,905,287 |
Oyler , et al. |
March 15, 2011 |
Methods of using a polymeric precipitate to reduce the loss of
fluid to a subterranean formation
Abstract
Methods are provided for reducing the loss of a wellbore
servicing fluid to a subterranean formation. A polymeric solution
and an activator may be contacted in the formation, thereby forming
a precipitate to at least partially block fluid from flowing
further into the formation. The fluid may be, for example, a
drilling fluid, a cement composition, a workover fluid, or
combinations thereof. The polymeric solution may comprise a
polyvinylpyrrolidone aqueous solution, and the activator may
comprise a formate brine. In one embodiment, the polymeric solution
and the activator are contacted before completing a drilling
operation in the wellbore. In another embodiment, they are
contacted before completing a primary cementing operation in the
wellbore. In yet another embodiment, they are contacted before
completing a secondary cementing operation in the wellbore. When
desirable, the precipitate may be easily and quickly removed from
the subterranean formation by dissolving it in fresh water.
Inventors: |
Oyler; Kenneth W. (Baytown,
TX), Thaemlitz; Carl J. (Katy, TX) |
Assignee: |
Halliburton Energy Services
Inc. (Duncan, OK)
|
Family
ID: |
37107367 |
Appl.
No.: |
11/109,354 |
Filed: |
April 19, 2005 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20060231255 A1 |
Oct 19, 2006 |
|
Current U.S.
Class: |
166/300; 166/294;
166/295; 175/64 |
Current CPC
Class: |
C09K
8/508 (20130101); C09K 8/501 (20130101) |
Current International
Class: |
E21B
43/25 (20060101); E21B 7/00 (20060101); E21B
33/00 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 188 856 |
|
Jul 1986 |
|
EP |
|
0 668 339 |
|
Feb 1995 |
|
EP |
|
1082046 |
|
Feb 1964 |
|
GB |
|
2 267 921 |
|
Dec 1993 |
|
GB |
|
WO 96/03474 |
|
Feb 1996 |
|
WO |
|
WO 96/04348 |
|
Feb 1996 |
|
WO |
|
WO96/04348 |
|
Feb 1996 |
|
WO |
|
WO 97/05212 |
|
Feb 1997 |
|
WO |
|
WO02/087749 |
|
Nov 2002 |
|
WO |
|
WO 2004/090067 |
|
Oct 2004 |
|
WO |
|
WO 2004/090067 |
|
Oct 2004 |
|
WO |
|
WO 2005/078047 |
|
Aug 2005 |
|
WO |
|
WO 2006/111703 |
|
Oct 2006 |
|
WO |
|
WO 2007/010212 |
|
Jan 2007 |
|
WO |
|
Other References
Halliburton brochure entitled "Accolade.TM. Drilling Fluid Exceeds
New GOM Environmental Standards and Boosts Performance" dated 2002.
cited by other .
Foreign communication from a related counterpart application, Jun.
1, 2005. cited by other .
Foreign communication from a related counterpart application, Dec.
21, 2004. cited by other .
Foreign communication from a related counterpart application, Sep.
13, 2004. cited by other .
Office Action from U.S. Appl. No. 10/411,015, Nov. 1, 2005. cited
by other .
Office Action from U.S. Appl. No. 10/411,015, Apr. 20, 2005. cited
by other .
Foreign communication from a related counterpart application, Sep.
25, 2006. cited by other .
Office Action from U.S. Appl. No. 11/109,150, Mar. 29, 2006. cited
by other .
Office Action from U.S. Appl. No. 10/776,887, Mar. 5, 2007. cited
by other .
Office Action from U.S. Appl. No. 10/776,887, Sep. 6, 2006. cited
by other .
Office Action from U.S. Appl. No. 10/776,887, May 22, 2006. cited
by other .
Foreign examination from a related application, May 29, 2007. cited
by other .
Office Action from U.S. Appl. No. 11/109,150, Sep. 21, 2007. cited
by other .
Notice of Allowance in U.S. Appl. No. 10/411,015, Apr. 21, 2006.
cited by other .
Office Action from U.S. Appl. No. 10/776,887, Feb. 6, 2008. cited
by other .
Office Action from U.S. Appl. No. 10/776,887, Aug. 23, 2007. cited
by other .
Office Action from U.S. Appl. No. 11/183,113, Feb. 6, 2008. cited
by other .
Office Action from U.S. Appl. No. 11/183,122, Feb. 6, 2008. cited
by other .
Foreign Communication from a Related Counterpart
Application--PCT/GB2005/000411, Aug. 14, 2006. cited by other .
Foreign Communication from a Related Counterpart
Application--PCT/GB2006/002622, Jan. 16, 2008. cited by other .
Foreign Communication from a Related Counterpart
Application--PCT/GB2006/001286, Oct. 23, 2007. cited by other .
Foreign Communication from a Related Counterpart
Application--PCT/GB2006/001286, Jun. 16, 2006. cited by other .
Foreign Communication from a Related Counterpart
Application--PCT/GB2006/001244, Oct. 23, 2007. cited by other .
Foreign Communication from a Related Counterpart
Application--PCT/GB2006/001244, Dec. 28, 2006. cited by other .
Office Action mailed Jun. 9, 2008 from U.S. Appl. No. 11/109,150.
cited by other .
Office Action mailed Aug. 11, 2008 from U.S. Appl. No. 10/776,887.
cited by other .
Office Action mailed Oct. 9, 2008, for U.S. Appl. No. 11/183,113.
cited by other .
Office Action for U.S. Appl. No. 10/776,887 dated May 11, 2009.
cited by other .
Office Action for U.S. Appl. No. 11/183,122, dated Jun. 15, 2009.
cited by other .
Office Action for U.S. Appl. No. 11/183,122, dated Oct. 1, 2009.
cited by other .
Definition of "Clay", Hawley's Condensed Chemical Dictionary, 14th
Edition, KNOVEL, publisher, Richard J. Lewis Sr., editor, 2002;
pages: Title and "Clay." cited by other .
VIVIPRINT: Products for Digital Printing & Imaging;
International Specialty Products; pp. 1-11; 2006. cited by other
.
Office Action for U.S. Appl. No. 11/183,122 dated Mar. 16, 2010.
cited by other .
Office Action for U.S. Appl. No. 11/109,150 dated Apr. 16, 2010.
cited by other .
European Office Action for Patent Application No. EP 06 764 969.9
dated Apr. 30, 2010. cited by other .
Notice of Allowance for U.S. Appl. No. 10/776,887 dated Jun. 28,
2010. cited by other .
Office Action for U.S. Appl. No. 11/109,150 dated Aug. 5, 2010.
cited by other .
Supplemental Notice of Allowability for U.S. Appl. No. 10/776,887
dated Jul. 2, 2010. cited by other .
Notice of Alowance for U.S. Appl. No. 11/183,122 dated Sep. 23,
2010. cited by other .
Foreign communciation related to a counterpart application dated
Dec. 28, 2006. cited by other .
Patent Application entitled "Wellbore Treatment Kits For Forming A
Polymeric Precipitate to Reduce the Loss of Fluid To A Subterranean
Formation" by Kenneth W. Oyler et al., filed Apr. 19, 2005, as U.S.
Appl. No. 11/109,150. cited by other .
U.S. Appl. No. 10/776,887, filed Oct. 14, 2004, Temple et al. cited
by other .
Foreign communication from a related counterpart application, Jun.
1, 2005. cited by other .
Foreign communication from a related counterpart application, Dec.
21, 2004. cited by other .
Foreign communication from a related counterpart application, Sep.
13, 2004. cited by other .
Office Action from U.S. Appl. No. 10/411,015, Nov. 1, 2005. cited
by other .
Foreign communication from a related counterpart application, Sep.
25, 2006. cited by other .
Baroid brochure entitled "BARACAT.RTM. Shale Stabilizer" dated
2002. cited by other .
Baroid brochure entitled "BARASIL.RTM. Shale Stabilizer" dated
2002. cited by other .
Baroid brochure entitled "BARO-TROL.RTM. Plus" dated 2000. cited by
other .
Baroid brochure entitled CLAYSEAL.RTM. Shale Stabilizer dated 2002.
cited by other .
Baroid brochure entitled "EZ-MUD.RTM. Shale Stabilizer" dated 2002.
cited by other .
Baroid brochure entitled "GEM.RTM. 2000 Shale Stabilizer" dated
2002. cited by other .
Baroid brochure entitled "HYDRO-GUARD.TM. Inhibitive Water-Based
Fluid" date Sep. 2002. cited by other .
Hood, David et al., "Structural Insights Into a Novel
Molecular-Scale Composite of Soluble Poly(vinyl pyrrolidone)
Supporting Uniformly Dispersed Nanoscale Poly(vinyl pyrrolidone)
Particles" dated Sep. 23, 2002. cited by other .
Nesbitt, L.E. et al., "Shale Stabilization Principles" SPE 14248,
dated Sep. 1985. cited by other .
International Specialty Products brochure entitled "New
ViviPrint.TM. Technology Commercially Available" dated 2002. cited
by other .
Zyvek brochure entitled "Nanotechnology" by Christine Peterson,
undated. cited by other .
Kodak brochure entitled "Nanoparticles and You--Chances are You've
Got Them" dated 2001. cited by other .
Poehlein, Gary "Connection to Other Fields; Education Issues,"
dated 1998. cited by other .
Baker Hughes Drilling Fluids, "Water Based Fluids: Max-Shield,"
available at
http://www.bakerhughes.com/DrillingFluids/water.sub.--based.sub.--flui-
ds/maxshield.htm, 2006. cited by other .
Baker Hughes Drilling Fluids, "Safety Data Sheet: Max-Shield", Oct.
27, 2004. cited by other .
Dye, Billy et al., "Design Considerations for High Performance
Water-Based Muds," American Association of Drilling Engineers,
AADE-04-DF-HO-14, Apr. 2004. cited by other .
Baker Hughes Drilling Fluids, Material Safety Data Sheet:
PERFORMAX.TM. , Nov. 13, 2003. cited by other .
U.S. Appl. No. 11/183,122, filed Jul. 15, 2005, Youngson et al.
cited by other .
U.S. Appl. No. 11/183,113, filed Jul. 15, 2005, Youngson et al.
cited by other .
U.S. Appl. No. 11/109,150, filed Apr. 19, 2005, Oyler et al. cited
by other.
|
Primary Examiner: Bates; Zakiya W
Assistant Examiner: Ditrani; Angela M
Attorney, Agent or Firm: Roddy; Craig W. McDermott, Will
& Emery
Claims
What is claimed is:
1. A method of treating a subterranean formation, the method
comprising: pumping a polymeric solution into the subterranean
formation; pumping an activator into the subterranean formation;
wherein a polymer comprising the polymeric solution and the
activator are separated while being pumped into the subterranean
formation; and wherein the activator comprises at least one brine
selected from the group consisting of: a formate brine, an acetate
brine, an oxalate brine, and combinations thereof; contacting the
polymeric solution and the activator within the subterranean
formation; allowing the contacted polymeric solution and the
activator to form a substantially impermeable precipitate within
the subterranean formation that at least partially blocks a flow of
a wellbore servicing fluid further into the subterranean formation;
and dissolving at least a portion of the substantially impermeable
precipitate.
2. The method of claim 1, wherein the wellbore servicing fluid
comprises at least one wellbore servicing fluid selected from the
group consisting of: a drilling fluid, a cement composition, a
workover fluid, and combinations thereof.
3. The method of claim 1, wherein the contacting is performed
before completing a drilling operation in the subterranean
formation.
4. The method of claim 1, wherein the contacting is performed
before completing a primary cementing operation in a wellbore
disposed in the subterranean formation.
5. The method of claim 1, wherein the contacting is performed
before completing a secondary cementing operation in a wellbore
disposed in the subterranean formation.
6. The method of claim 1, wherein the contacting is performed
during a workover operation.
7. The method of claim 1, wherein the polymeric solution comprises
polyvinylpyrrolidone in water.
8. The method of claim 1, wherein a spacer separates the polymeric
solution and the activator as they are pumped into the subterranean
formation.
9. The method of claim 8, wherein the spacer comprises at least one
spacer selected from the group consisting of: a natural
hydrocarbon, a synthetic hydrocarbon, a glycol, a surfactant, fresh
water, and combinations thereof.
10. The method of claim 8, wherein the polymeric solution, the
spacer, and the activator are sequentially pumped into the
subterranean formation.
11. The method of claim 8, wherein the activator, the spacer, and
the polymeric solution are sequentially pumped into the
formation.
12. The method of claim 1, wherein the polymeric solution comprises
the activator and the polymer is coated with a material that
initially prevents the polymer and the activator from contacting
one another but dissolves over a period of time, such that after
the period of time, the polymer and the activator contact to form
the precipitate.
13. The method of claim 1, wherein a volume ratio of the polymeric
solution to the activator is in a range of from about 50:50 to
about 70:30.
14. The method of claim 1, wherein the polymer is in a range of
from about 1% to about 90% by weight of the polymeric solution.
15. The method of claim 1, wherein the activator comprises
potassium formate in an amount in a range of from about 10% to
about 78% by weight of the total formate brine.
16. The method of claim 1, further comprising removing the
precipitate from the subterranean formation by dissolving the
precipitate in water.
17. The method of claim 1, wherein the polymeric solution and the
activator are contacted within the subterranean formation before or
during the flow of the wellbore servicing fluid.
18. A method of treating a wellbore that penetrates a subterranean
formation, the method comprising: pumping a polymeric solution into
the subterranean formation; pumping an activator into the
subterranean formation; wherein a polymer comprising the polymeric
solution and the activator are separated while being pumped into
the subterranean formation; and wherein the activator comprises at
least one brine selected from the group consisting of: a formate
brine, an acetate brine, an oxalate brine, and combinations
thereof; contacting the activator and the polymeric solution within
the subterranean formation, thereby forming a substantially
impermeable precipitate within the subterranean formation that at
least partially blocks a flow pathway into the subterranean
formation; circulating a wellbore servicing fluid through the
wellbore; and dissolving at least a portion of the substantially
impermeable precipitate.
19. The method of claim 18, further comprising introducing a spacer
fluid to the wellbore in between the activator and the polymeric
solution.
20. The method of claim 18, wherein the polymeric solution
comprises polyvinylpyrrolidone in water.
21. A method of drilling a wellbore at least partially through a
subterranean formation, the method comprising: pumping a polymeric
solution into the subterranean formation; pumping an activator into
the subterranean formation; wherein a polymer comprising the
polymeric solution and the activator are separated while being
pumped into the subterranean formation; and wherein the activator
comprises at least one brine selected from the group consisting of:
a formate brine, an acetate brine, an oxalate brine, and
combinations thereof; contacting the activator and the polymeric
solution within the subterranean formation, thereby forming a
substantially impermeable precipitate within the subterranean
formation that at least partially blocks a flow pathway into the
subterranean formation; applying torque to a bit within the
wellbore while applying force to urge the bit to extend through the
subterranean formation; circulating a drilling fluid past the bit
to remove cuttings therefrom; and dissolving at least a portion of
the substantially impermeable precipitate.
22. A method comprising: pumping a polymeric solution into a
subterranean formation; wherein the polymeric solution comprises
polyvinylpyrrolidone in water; pumping an activator into the
subterranean formation; wherein the activator comprises at least
one brine selected from the group consisting of: a formate brine,
an acetate brine, an oxalate brine, and combinations thereof;
contacting the polymeric solution and the activator within the
subterranean formation, thereby forming a substantially impermeable
precipitate within the subterranean formation that at least
partially blocks a flow pathway into the subterranean formation;
and dissolving at least a portion of the substantially impermeable
precipitate.
23. The method of claim 22, further comprising circulating a
wellbore servicing fluid through the subterranean formation.
24. The method of claim 22, further comprising: applying torque to
a bit within a wellbore penetrating the subterranean formation
while applying force to urge the bit to extend through the
subterranean formation; and circulating a drilling fluid past the
bit to remove cuttings therefrom.
25. The method of claim 22, wherein a spacer separates the
polymeric solution and the activator as they are pumped into the
subterranean formation.
Description
FIELD OF THE INVENTION
The present invention generally relates to downhole operations, and
more particularly to methods of forming a polymeric precipitate in
a subterranean formation to reduce the loss of fluid to the
formation.
BACKGROUND OF THE INVENTION
The following paragraphs contain some discussion, which is
illuminated by the innovations disclosed in this application, and
any discussion of actual or proposed or possible approaches in this
Background section does not imply that those approaches are prior
art.
Natural resources such as oil or gas residing in a subterranean
formation can be recovered via the formation of wells that
penetrate the formation. In particular, a wellbore is typically
drilled down to the formation while circulating a drilling fluid
(also known as a drilling mud) through the wellbore. During the
drilling process, the drill bit generates drill cuttings that
consist of small pieces of shale and rock. The drilling fluid
carries the drill cuttings in a return flow stream back to the well
drilling platform. After terminating the circulation of the
drilling fluid, a string of pipe, e.g., casing, is run into the
wellbore. The drilling fluid is then usually circulated downwardly
through the interior of the pipe and upwardly through the annulus,
which is located between the exterior of the pipe and the walls of
the well bore.
Primary cementing is then usually performed whereby a cement slurry
is pumped down through the string of pipe and into the annulus
between the string of pipe and the walls of the wellbore to allow
the cement slurry to set into an impermeable cement column and
thereby seal the annulus. Subsequent secondary cementing
operations, i.e., cementing operations occurring after the primary
cementing operation, may also be performed. One example of a
secondary cementing operation is squeeze cementing whereby a cement
slurry is forced under pressure to areas of lost integrity in the
annulus to seal off those areas.
Unfortunately, the fluids used in such downhole operations may be
lost to the subterranean formation while circulating the fluids in
the wellbore. In particular, the fluids may enter the subterranean
formation via depleted zones, zones of relatively low pressure,
naturally occurring fractures, weak zones having fracture gradients
exceeded by the hydrostatic pressure of the drilling fluid, and so
forth. As a result, the services provided by the fluids are more
difficult to achieve. For example, a problem known as lost
circulation may occur in which the circulation of the drilling
fluid in the wellbore drops due to it being lost to the formation.
Its circulation may eventually become too low to allow for further
drilling of the wellbore. Also, a cement slurry may be lost to the
formation as it is being placed in the annulus, thereby rendering
it ineffective in isolating the adjacent subterranean formation. In
particular, the amount of cement slurry may be insufficient to fill
the annulus from top to bottom during primary cementing or to fill
areas of lost integrity in a pre-existing cement column during
secondary cementing. Further, dehydration of the cement slurry may
result, compromising the strength of the cement that forms in the
annulus.
Traditional methods of overcoming the problems described above
include sealing the zones through which the fluids can enter the
subterranean formation with thixotropic cements, non-aqueous
dispersions of clays, sodium silicate solutions in combination with
calcium salt sweeps, and fluids containing inert platelets such as
mica. However, the presence of such sealants in the formation may
block the flow of oil or gas into the wellbore when it is desirable
to begin production. Further, those materials may contaminate fresh
water produced by the formation ahead of the oil or gas.
Unfortunately, the sealants typically cannot be easily removed from
the formation before production. A need therefore exists to develop
a way to prevent the loss of fluid to the subterranean formation
without adversely affecting the production of water, oil, or gas by
the formation.
SUMMARY OF THE INVENTION
Some teachings and advantages found in the present application are
summarized briefly below. However, note that the present
application may disclose multiple embodiments, and not all of the
statements in this Summary section necessarily relate to all of
those embodiments. Moreover, none of these statements limit the
claims in any way.
In embodiments, methods of treating a subterranean formation
comprise contacting a polymeric solution and an activator in the
subterranean formation, thereby forming a precipitate to at least
partially block a flow of a wellbore servicing fluid further into
the formation. The wellbore servicing fluid may be, for example, a
drilling fluid, a cement composition, a workover fluid, or
combinations thereof. The polymeric solution may comprise, for
example, a polyvinyl pyrrolidone aqueous solution, and the
activator may comprise, for example, a formate brine. In one
embodiment, the polymeric solution and the activator are contacted
before completing a drilling operation in the wellbore. In another
embodiment, they are contacted before completing a primary
cementing operation in the wellbore. In yet another embodiment,
they are contacted before completing a secondary cementing
operation in the wellbore. When desirable, the precipitate may be
easily and quickly removed from the subterranean formation by
dissolving it in fresh water.
In additional embodiments, methods of treating a wellbore that
penetrates a subterranean formation comprise: introducing an
activator to the wellbore; introducing a polymeric solution in situ
with the activator, thereby forming a hard precipitate to at least
partially block a flow pathway into the subterranean formation;
circulating a wellbore servicing fluid through the wellbore; and
dissolving the precipitate to prepare for hydrocarbon
production.
In more embodiments, methods of drilling a wellbore at least
partially through a subterranean formation comprise: introducing an
activator to the wellbore; introducing a polymeric solution in situ
with the activator, thereby forming a hard precipitate to at least
partially block a flow pathway into the subterranean formation; and
applying torque to a bit within the wellbore while applying force
to urge the bit to extend through the wellbore; and circulating a
drilling fluid past the bit to remove cuttings therefrom.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A is a side plan view of a drilling rig and a wellbore in the
earth for recovering oil from a subterranean formation.
FIG. 1B is a detailed view of a section of the wellbore depicted in
FIG. 1A, showing a precipitate blocking a flow pathway into the
subterranean formation.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
A polymeric solution and an activator may be contacted in a
subterranean formation in such a manner as to form a hard
precipitate in the formation. As used herein, a "polymeric
solution" is defined as a solution comprising a polymer, an
oligomer, or combinations thereof. As used herein, an "activator"
is defined as a material that, when present in a sufficient amount,
can cause the polymer and/or oligomer to precipitate out of the
solution, wherein the activator may be a liquid in which the
polymer and/or oligomer is insoluble. It is understood that
"subterranean formation" encompasses both areas below exposed earth
or areas below earth covered by water such as sea or ocean water.
The resulting polymeric precipitate is typically impermeable to
fluid and thus may form a barrier in the formation that at least
partially blocks one or more flow pathways through which a fluid
could undesirably migrate into the formation. Examples of such flow
pathways include natural or induced fractures, depleted zones,
zones of relatively low pressure, weak zones having fracture
gradients exceeded by the hydrostatic pressure of the fluid being
used to service the wellbore, perforations formed by a perforating
gun, and combinations thereof.
The polymeric solution and the activator typically reach the
subterranean formation by pumping them down a wellbore that
penetrates the formation. The presence of the precipitate barrier
in the formation allows fluids (known as wellbore servicing fluids)
to be circulated or squeezed in the wellbore for the purpose of
servicing the wellbore without being concerned that a substantial
amount of the fluid could flow into and be lost to the formation.
FIGS. 1A and 1B illustrate how the precipitate forms a barrier to
at least partially reduce the flow of fluid far into a subterranean
formation. FIG. 1A depicts a wellbore 10 that has been drilled in
the earth such that it penetrates a subterranean formation. An oil
rig 30 positioned near the surface of the earth 20 may be used to
recover oil from the formation. A pipe 40, e.g., a drill pipe or
tubing, may extend down through wellbore 10 for delivering fluid to
and/or from the wellbore. FIG. 1B illustrates a section 50 of
wellbore 10 in detail. As illustrated in FIG. 1B, a precipitate 60
forms a solid coating across a flow pathway 70 such as a crack
within wellbore 10 and thereby seals flow pathway 70. The larger
the quantity of polymer solution pumped into wellbore 10, the
thicker the coating formed therein. In an embodiment, the coating
may have a thickness ranging from about 1 millimeter to about 10
millimeters. Also, from about 0.25 to about 0.5 gram/cubic
centimeter of precipitate 60 may extend across flow pathway 70.
Precipitate 60 is desirably impermeable to fluid and thus inhibits
fluid from passing through pathway 70 and deeper into the adjacent
subterranean formation. Thus, precipitate 60 serves to reduce the
loss of such fluid to the formation, allowing it to be primarily
retained within wellbore 10 as it is pumped therethrough.
It is believed that the coating formed by the precipitate will be
effective in cracks that are both larger and smaller than the
coating thickness near the wall of the wellbore. That is, cracks
within the subterranean formation usually decrease in size at
greater depths within the formation. Thus, the polymer solution may
be pumped into cracks larger than the ensuing coating thickness to
a depth where the cracks become sufficiently narrow to allow the
coating to plug the entire crack.
In an embodiment, a spacer separates the polymeric solution and the
activator as they are being pumped downhole. As used herein,
"spacer" is defined as a fluid that prevents the polymeric solution
and the activator from interacting with each other as they pass
down the wellbore and that is inert with respect to the polymeric
solution and the activator. Examples of suitable fluids to use as
spacers include natural hydrocarbons, synthetic hydrocarbons,
surfactants, glycols, fresh water, and combinations thereof. The
amount of the spacer employed in this embodiment may range from
about 1 to about 5 barrels or alternatively may be about 2 barrels.
In one embodiment, the polymeric solution, the spacer, and the
activator are sequentially pumped to the formation. In another
embodiment, the activator is pumped first and the polymeric
solution is pumped behind the spacer. Within the subterranean
formation, the polymeric solution and the activator are no longer
separated and thus contact each other, resulting in the formation
of the precipitate.
The polymeric solution and the activator may be displaced into the
wellbore before or during the circulation/squeezing of a wellbore
servicing fluid in the wellbore. In an embodiment, they may be
pumped downhole after the discovery that at least a portion of the
wellbore servicing fluid is being lost to the subterranean
formation. At this point, the circulation/squeezing of the wellbore
servicing fluid in the wellbore may be terminated to allow for the
formation of the precipitate within the formation. Once the
precipitate has been formed, the circulation/squeezing of the fluid
in the wellbore may then be resumed. The formation of the
precipitate may occur within 1 minute of the initial contact
between the polymeric solution and the activator. However,
typically one waits for a period of in a range of from about 30
minutes to about 4 hours before passing the wellbore servicing
fluid into the wellbore again.
In one embodiment, the precipitate may be used to reduce a
pre-completion loss to a subterranean formation. As used herein, a
"pre-completion loss" refers to a loss of fluid to a subterranean
formation that occurs before the wellbore is completed, i.e.,
before the annulus of the wellbore has been sealed by a sealant
composition, e.g., a cement composition. In an embodiment, the
pre-completion loss is the loss of a drilling fluid during its
circulation through a wellbore both during and after the drilling
of the wellbore. In another embodiment, the pre-completion loss is
the loss of a cement slurry (or other type of sealant composition)
during primary cementing.
In another embodiment, the precipitate may be used to prevent a
post-completion loss to the subterranean formation. As used herein,
a "post-completion" loss refers to a loss of fluid to a
subterranean formation that occurs after the wellbore is completed,
i.e., after the annulus of the wellbore has been sealed by a
sealant composition, e.g., a cement composition. In an embodiment,
the post-completion loss may be that of a secondary sealant
composition such as a cement composition. By way of example, the
secondary sealant composition may be placed in one or more
permeable zones present in the wellbore using a squeeze technique
known in the art. The permeable zones may extend, for example,
through the wall of a conduit positioned in the wellbore, a
sealant/cement column in the annulus of the wellbore, a
microannulus of the wellbore, or combinations thereof. Examples of
those permeable zones include a fissure, a crack, a fracture, a
streak, a flow channel, a void, and combinations thereof. In yet
another embodiment, the post-completion loss may be the loss of a
fluid, e.g., a workover fluid, during a production enhancement
operation, e.g., a workover operation.
In certain situations, it may be desirable to remove the polymeric
precipitate from the subterranean formation. For instance, the
precipitate may be removed to prepare the formation for the
production of oil, gas, and/or water. That is, the precipitate may
be removed to prevent it from blocking the flow of such natural
resources from the formation. It may also be removed to avoid
contaminating any water produced by the formation. In an
embodiment, the precipitate may be removed by dissolving it in a
fluid in which it is soluble such as fresh water, thereby providing
a simple and inexpensive way to eliminate the precipitate. For
example, the precipitate may be removed by water that is initially
produced by the formation, or alternatively, it may be removed by
water that is intentionally pumped into the wellbore. Examples of
compounds that may be employed to dissolve the precipitate include
but are not limited to fresh water and brines such as halide
brines, e.g., sodium chloride brine.
The methods described above for reducing the loss of a wellbore
servicing fluid to the subterranean formation utilize a polymeric
solution and an activator. The volume ratio of the polymeric
solution to the activator may be in a range of from about 50:50 to
about 70:30. The polymeric solution comprises a polymer and a fluid
in which the polymer has a relatively high solubility. In
embodiments, the polymeric solution may also include but is not
limited to lost circulation materials, weighting agents such as
barite, acid soluble particles, and combinations thereof. An
example of a suitable polymeric solution includes
polyvinylpyrrolidone (PVP) in water, which is commercially
available from ISP Technologies, Inc. under the tradename of
VIVIPRINT 540 solution (10% PVP by weight of the aqueous solution)
and from Halliburton Energy Services, Inc. under the tradename of
PERFORMATROL polymer (10% PVP by weight of the aqueous solution).
The amount of the polymer in the polymeric solution may be a range
of from about 1% to about 90%, alternatively from about 5% to about
50%, by weight of the polymeric solution. Examples of suitable
activators include formate brines (e.g., potassium formate, sodium
formate, and cesium formate), acetate brines (e.g., potassium
acetate, sodium acetate, and cesium acetate), oxalate brines (e.g.,
potassium oxalate, sodium oxalate, and cesium oxalate), halide
brines (e.g., zinc bromide), and combinations thereof. In an
embodiment, the amount of the potassium formate in the activator
may be in a range of from about 10% to about 78%, or alternatively
from about 50% to about 78%, by weight of the total formate
brine.
Modifications to the Foregoing Embodiments
In an alternative embodiment, the activator may also serve as the
solvent in which the polymer is dissolved. The polymer may be
coated with a material that prevents it from initially contacting
the activator/solvent. Thus, the polymer and the activator may be
concurrently pumped downhole without forming a precipitate. The
coating may eventually dissolve such that the activator/solvent
contacts the polymer and thus forms the precipitate. The period of
time required for the coating to completely dissolve may be
sufficient to allow the polymer to be pumped into a crack or void
in a subterranean formation. As a result, the formation of the
precipitate is time delayed.
EXAMPLES
The invention having been generally described, the following
examples are given as particular embodiments of the invention and
to demonstrate the practice and advantages thereof. It is
understood that the examples are given by way of illustration and
are not intended to limit the specification or the claims to follow
in any manner.
Example 1
Several samples of a PERFORMATROL solution (i.e., the PVP solution)
were used in this example. About 16 lbs/gal of barite weighting
agent were added to each PERFORMATROL solution sample. The
PERFORMATROL solution samples remained pumpable after the addition
of the barite weighting agent.
Various potassium formate brines (i.e., the activator) having
different densities were combined with respective PERFORMATROL
solution samples. The volume ratio of the potassium formate to the
PERFORMATROL solution in each sample was 50:50. The densities of
the potassium formate brine were 9.8 lb/gal, 10.3 lb/gal, 10.8
lb/gal, 11.7 lb/gal, and 12.2 lb/gal. These particular densities of
the potassium formate brines caused a relatively hard PVP
precipitate to form. It is believed that potassium formate brines
having densities lower than 9.5 lb/gal will not form such a
precipitate.
As shown in Table 1 below, various properties of the precipitate
formed using the 13.2 lb/gal potassium formate brine were
determined. For each mL of PERFORMATROL solution used,
approximately 0.4 mL of the potassium formate brine was required to
precipitate all of the PVP. The precipitate formed within 1 minute
of contacting the PERFORMATROL solution with the formate brine. The
sealing capability of the precipitate was determined by placing it
on a slotted disk and then placing the disk in a filtration
apparatus. A drilling mud was then placed on the disk and an
attempt was made to filter the mud through the precipitate by
applying a pressure of 500 psi across the disk. The precipitate
withstood a 500 psi differential such that no mud could pass
through the precipitate at this pressure. The thickness of the seal
was measured as 1/8 inch. The precipitate was also heated on a
hotplate to determine the temperatures at which it is stable. The
precipitate exhibited no apparent decomposition at temperatures
less than or equal to 250.degree. F.
TABLE-US-00001 TABLE 1 Precipitate Properties Sealing Capability
500 psi Thickness 1/8 inch Rate of formation <1 min. Temperature
Stability .ltoreq.250.degree. F.
In addition, the lengths of time required to dissolve the
precipitate by contacting it with fresh water (placing it in about
100 mL), non-aqueous drilling muds, and halide brines were
compared, as presented in Table 2 below. It is noted that ACCOLADE
drilling mud is commercially available from Halliburton Energy
Services, Inc.
TABLE-US-00002 TABLE 2 Fluid Time to dissolve ACCOLADE base oil
Never dissolved 10.5 lb/gal ACCOLADE mud Never dissolved Freshwater
10 minutes Sodium Chloride brine (10 ppg) 15 minutes Sodium Bromide
brine (12.5 ppg) 2 hours Calcium Chloride brine (11.6 ppg) 12 hours
Calcium Bromide brine (14.2 ppg) 24+ hours
Based on Table 2, the precipitate can be dissolved relatively
quickly with freshwater or sodium chloride brine. Further, it may
also be removed at a relatively slow rate with calcium chloride
brine or calcium bromide brine. It is desirably insoluble in the
ACCOLADE drilling mud.
Example 2
The procedure followed in Example 1 was repeated with different
activators. More specifically, the potassium formate brines were
replaced with sodium formate brines, cesium formate brines, and
zinc bromide brines. All of those brines caused the PVP to
precipitate out of solution.
While preferred embodiments of the invention have been shown and
described, modifications thereof can be made by one skilled in the
art without departing from the spirit and teachings of the
invention. The embodiments described herein are exemplary only, and
are not intended to be limiting. Many variations and modifications
of the invention disclosed herein are possible and are within the
scope of the invention.
Accordingly, the scope of protection is not limited by the
description set out above but is only limited by the claims which
follow, that scope including all equivalents of the subject matter
of the claims. Each and every claim is incorporated into the
specification as an embodiment of the present invention. Thus, the
claims are a further description and are an addition to the
preferred embodiments of the present invention. The discussion of a
reference herein is not an admission that it is prior art to the
present invention, especially any reference that may have a
publication date after the priority date of this application. The
disclosures of all patents, patent applications, and publications
cited herein are hereby incorporated by reference, to the extent
that they provide exemplary, procedural, or other details
supplementary to those set forth herein.
* * * * *
References